1. ‘Garbage In, Garbage Out’ — usually said in
response to lusers who complain that a program
didn't “do the right thing” when given imperfect input or
otherwise mistreated in some way. Also commonly used to describe failures
in human decision making due to faulty, incomplete, or imprecise data.

2. Garbage In, Gospel Out:
this more recent expansion is a sardonic comment on the tendency human
beings have to put excessive trust in ‘computerized’
data.